The invention relates to a compound which is suited to act as pepstatin A analogue for the purpose of a protease inhibitor. The invention further relates to a use of such a compound, a method for synthesizing such a compound and the use of a double protected statine.
Pepstatin A is a potent inhibitor of secreted aspartic proteinases (Saps), particularly of Saps of Candida albicans. Saps are one of the most important virulence factors during infections of Candida albicans and play also important rules during infections caused by other pathogens, such as viruses, bacteria and protozoa.
Inhibiting the Saps is a powerful tool in treating Sap-related diseases. Though pepstatin A is a potent inhibitor of Saps, it cannot be used as a medicament due to its toxicity and rapid clearance in the body.
In the mid of the 90s of the 20th century, novel medicaments have been introduced to treat HIV (human immunodeficiency virus) infections, the so-called HIV protease inhibitors. In the context of this so-called intensified therapy it was recognized that oral candidiasis, being hitherto the most frequently occurring opportunistic infection in the course of an HIV infection, was observed much rarely in patients suffering from HIV infection (Hoegl L, Thoma-Greber E, Röcken M, Korting H C: HIV protease inhibitors influence the prevalence of oral candidosis in HIV-infected patients: a 2-year study. Mycoses 1998; 41:321-325).
Firstly, this reduction in occurrence of manifest oral candidiasis was thought to be based on an ameliorated immune defense due to the novel HIV therapy. Later, it was assumed that due to a structural relationship between HIV protease and Saps of Candida albicans also direct influences on the Saps as targets might be possible.
This assumption was experimentally tested. In 1999, it was published that HIV protease inhibitors saquinavir and indinavir influence the in vitro activity of Saps of Candida albicans isolates of HIV infected patients by means of inhibitory activity (Korting H C, Schaller M, Eder G, Hamm G, Böhmer U, Hube B: Effects of the human immunodeficiency virus (HIV) proteinase inhibitors saquinavir and indinavir on in vitro activities of secreted aspartyl proteinases of Candida albicans isolates from HIV-infected patients. Antimicrob. Ag. Chemother. 1999; 43:2038-2042).
Similar in vitro results were published by Cassone et al. (Cassone A, De Bernardis F, Torosantucci A, Tacconelli E, Tumbarello M, Cauda R: In vitro and in vivo anticandidal activity of human immunodeficiency virus proteins inhibitors. J. Infect. Dis. 1999; 180:448-453). Further, another publication was directed to the use of HIV-1 protease inhibitors such as ritonavir, saquinavir and indinavir to inhibit Saps of Candida albicans (Monod M, Borg-von Zepelin M, Telenti A, Sanglard D. The inhibition of Candida-albicans-secreted aspartic proteases by three different HIV protease inhibitors. Dermatology. 1999; 198(4):412-414).
The phenomenon of reducing the occurrence of oral candidiasis after introducing protease inhibitors was also described by Hood et al. with respect to observations of a single patient (Hood S, Bonington A, Evans J, Denning D: Reduction in oropharyngeal candidiasis following introduction of protease inhibitors. AIDS 1998; 12:447-448).
In 2000, a study was published according to which the influence of HIV protease inhibitor therapy on HIV-associated oropharyngeal candidiasis was confirmed, although is was explained by an amelioration of immune defense (Arribas J R, Hernández-Albujar S, González-Garcia J J, Peñ a J M, Gonzalez A, Cañedo T, Madero R, Vazquez J J, Powderly W G: Impact of protease inhibitor therapy on HIV-related oropharyngeal candidiasis. AIDS 2000; 14:979-985).
But as early as in 1999, it was shown in the context of a case control study that influencing the reoccurring oral candidiasis by HIV protease inhibitors cannot be explained only with an amelioration of immune defense (Cauda R, Tacconelli E, Tumbarello M, Morace G, De Bernardis F, Torosantucci A, Cassone A: Role of protease inhibitors in preventing recurrent oral candidosis in patients with HIV infection: a prospective case-control study. J. Acquir. Immune Defic. Syndr. 1999; 21:20-25).
In the following, it was shown that fungicides like fluconazole, which are usually used to treat oral candidiasis in the context of an HIV infection, do not significantly influence Saps of Candida albicans. A positive result could only be shown for the topic fungicide ciclopiroxolamin which is not used within the oral cavity (Schaller M, Krnjaic N, Niewerth M, Hamm G, Hube B, Korting H C: Effect of antimycotic agents on the activity of aspartyl proteinases secreted by Candida albicans. J. Med. Microbiol. 2003; 52:247-249).
In 2002, a publication dealt with Saps as being a novel pharmaceutical target for treatment of candidiasis (Bein M, Schaller M, Korting H C: The secreted aspartic proteinases as a new target in the therapy of candidiasis. Curr. Drug Targets 2002; 3:351-357). Also, works of Abad-Zapatero done in the company Abbot (USA) have been found very interesting (Stewart K, Abad-Zapatero C: Candida proteases and their inhibition: prospects for antifungal therapy. Curr. Med. Chem. 2001; 8:941-948).
Already prior to this, the crystal structure of isoenzyme 2 of Saps was solved (Cutfield S M, Dodson E J, Anderson B F, Moody P C, Marshall C J, Sullivan P A, Cutfield J F: The crystal structure of a major secreted aspartic proteinase from Candida albicans in complexes with two inhibitors. Structure 1995; 3:1261-1271).
Amongst others, Schaller et al. worked on the pathogenic relevance of Saps as main virulence factors of Candida albicans (Schaller M, Korting H C, Schäfer W, Bastert J, Chen W, Hube B: Secreted aspartic proteinase (Sap) activity contributes to tissue damage in a model of human oral candidosis. Mol. Microbiol. 1999; 34:169-180).
Structural aspects of the targets have also been considered, in particular by means of molecular modelling (Hoegl L, Korting H C, Klebe G: Inhibitors of aspartic proteases in human diseases: molecular modeling comes of age. Pharmazie 1999; 54:319-329).
Further, the three-dimensional structure of other Sap isoenzymes has been solved, namley that of Sap3 (Borelli C, Ruge E, Schaller M, Monod M, Korting H C, Huber R, Maskos K: The crystal structure of the secreted aspartic proteinase 3 from Candida albicans and its complex with pepstatin A. Proteins 2007; 68:738-748) as well as that of Sap1 and of Sap5 (Borelli C, Ruge E, Lee J H, Schaller M, Vogelsang A, Monod M, Korting H C, Huber R, Maskos K: X-ray structure of Sap1 and Sap5: Structural comparison of the secreted aspartic proteinases from Candida albicans. Proteins 2008; 72:1308-1319).
Various pepstatin A derivatives have been described which are effective against at least some of Saps of Candida species in lower concentration than that needed in case of Sap inhibition by HIV-1 protease inhibitors (Pichová I, Pavlicková L, Dostál J, Dolejsí E, Hrusková-Heidingsfeldová O, Weber J, Ruml T, Soucek M. Secreted aspartic proteases of Candida albicans, Candida tropicalis, Candida parapsilosis and Candida lusitaniae. Inhibition with peptidomimetic inhibitors. Eur. J. Biochem. 2001; 268(9):2669-2677; Majer F, Pavlicková L, Majer P, Hradilek M, Dolejsí E, Hrusková-Heidingsfeldová O, Pichová I. Structure-based specificity mapping of secreted aspartic proteases of Candida parapsilosis, Candida albicans, and Candida tropicalis using peptidomimetic inhibitors and homology modeling. Biol. Chem. 2006 September; 387(9):1247-1254.).
WO 94/24150 A2 and WO 96/12738 A2 describe further pepstatin A derivatives or analogues to be used as Sap inhibitors, though data concerning the efficacy of those pepstatin derivatives are not disclosed.
JP 54-163826 A describes two pepstatin A derivatives to be used as antihypertensives.